1. Field of the Invention
This invention relates to a developing unit for an electrophotographic apparatus.
2. Discussion of the Related Art
In a developing unit using a two-component developer, sometimes carrier as well as toner sticks onto the surface of a photosensitive body in developing a latent image formed in the photosensitive body. In order to remove the carrier, the developing unit is provided with a recovery roll.
In an electrophotographic apparatus in which the carrier recovered with a recovery roll is returned to the developing unit, a gap is defined between the outer surface of the recovery roll and the inner surface of the developing unit, which is large enough for the recovered carrier to pass through. Hence, the developer may be scattered out of the developing unit through the gap. In order to overcome this difficulty, heretofore the gap is closed with a sealing member made of a polyester film or the like.
If, in the electrophotographic apparatus, toner stuck on the recovered carrier is caught between the recovery roll and the sealing member, then the toner is melted by the frictional heat produced by the rotation of the recovery roll, as a result of which the toner'grain size increases. If the toner with increased grain size is mixed with the developer at the developing unit, then it is used in the developing operation. In such a case, the resultant print is lowered in print quality.